Expose util functions on scripts & buffers.

Correction: buffer's codepoints are all Chars.

Reimplement parts of Harfbuzz where that's easier than writing a binding.

Removed a note where that turned out not to be the case.

Integrate guessing chars, document properties, expose default property values.

Implement conversion from functional Buffers to imperative Buffers.

FreeType integration is not threadsafe, not that in API design.

Design FreeType2 integration.

Draft pure-functional Harfbuzz API.